Age estimation of puppies based on the radiographically assessed development of ossification centres in the carpal and metacarpal regions

Abstract Background The need for proper age determination in puppies has increased enormously due to the growing illegal trade in puppies that are too young to be removed from the litter or too young to have been properly vaccinated against rabies. Methods Dorsopalmar and mediolateral radiographs of the (meta)carpal region, either taken from puppy cadavers or from the Faculty's patient database, were studied in a cross‐sectional study of 252 puppies of various sizes, aged 6–212 days. The appearance and development of ossification centres as a function of age in five regions of interest in the (meta)carpal region were scored using a two‐ to six‐step scoring system based on shape and delineation. Results A positive correlation with age was found for all investigated regions. Intra‐ and interrater agreement between two observers was excellent, except for the distal epiphyses of the metacarpal bones. Postnatal ossification started after the second week of life with the carpal bones, closely followed by the radial trochlea. All ossification centres were present in all puppies from 84 days, except for the sesamoid bone in the tendon of the long abductor muscle of the first digit. Timing of appearance differed significantly between different sized breeds. There were no significant differences between the sexes. Limitations Age distribution was not balanced for all breed size classes. Conclusions The radiographic timing of the appearance and development of ossification centres in the carpal region is a promising method for age estimation in puppies.